IMO C
Let O be the center.
arc ABC = 24 cm
The exterior angle substended by A and C at O is 120 + 120 = 240 (see the picture below)
Thus 240 deg --> 24 cm
Full circle 360 deg --> 36cm
So (pie)*(Diameter) = 36
=> Diameter = 36/(3.14) = 11.46
BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course
Redeem
Target Test Prep GMAT OnDemand
Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.
- 715+ score guarantee — highest in the industry (99th percentile)
- 52 chapters · 1,500+ lessons · 4,000+ practice questions
- 400 hours of video · 1,500+ instructor-led HD smartboard lessons
- 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
- 24/7 live support + weekly Zoom office hours with GMAT instructors
- TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
- 1,200+ flashcards + AI-powered study assistant & daily calendar
- OnDemand, LiveTeach & GMAT Bootcamp formats available
- Also: GRE, SAT Math & Executive Assessment courses
- MBA Admissions Consulting now available
- 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
- 200,000+ students served
- 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★
5.0
(559 reviews)
130-pt guarantee
$0 to start
then $127/mo
gmat prep
Source: Beat The GMAT — Problem Solving |
easier way if i may:
If the triangle is equalateral...that means each arc 1/3rd lengh is equal..total arc length for 2/3rds of the circumference is 24, so C = 36
C= 2piR we can have r = C/2pi -> 2R is the answer which is 11.4sh
If the triangle is equalateral...that means each arc 1/3rd lengh is equal..total arc length for 2/3rds of the circumference is 24, so C = 36
C= 2piR we can have r = C/2pi -> 2R is the answer which is 11.4sh
Always Welcome!!5abi wrote:easier way if i may:
If the triangle is equalateral...that means each arc 1/3rd lengh is equal..total arc length for 2/3rds of the circumference is 24, so C = 36
C= 2piR we can have r = C/2pi -> 2R is the answer which is 11.4sh
If the problem is Easy Respect it, if the problem is tough Attack it
5abi wrote:easier way if i may:
If the triangle is equalateral...that means each arc 1/3rd lengh is equal..total arc length for 2/3rds of the circumference is 24, so C = 36
C= 2piR we can have r = C/2pi -> 2R is the answer which is 11.4sh
thank you very much......... for simple method...












